One of the primary factors limiting the current techniques for the in vivo analysis of human movement is the placement of measuring devices on the skin surface in an attempt to evaluate underlying bone movement. The current methods produce an unknown artifact associated with the relative movement of the skin with respect to the bone. The goal of this project is to develop a method which will account for both the rigid body and deformable components of the movement of a limb segment using markers placed on the surface of the skin. Preliminary work with a new method described as a Point Cluster Technique (PCT) has suggested that the method has the potential to produce increased reliability when applied to the analysis of human movement. The method provides a parameter, the eigenvalues of the inertia tensor, which remain invariant if the cluster of points move as a rigid body. The nonrigid body motion artifacts can be minimized using these eigenvalues as a criteria. The goals of the present proposal are to examine methods of applying this technique using two approaches to the optimization of the methodology previously developed.